Underground water tank contamination or loss
An underground tank that is losing water or showing contamination has a two-way problem: stored water escaping, and groundwater entering. Where it stores drinking water, ingress is a health issue and needs treating as urgent rather than routine.
This can compound quickly or carries a safety risk. Do not wait for the monsoon to end.
Probable causes, ranked
Ordered by how often we find each one to be the actual source. The 'tell' is what distinguishes it from the others.
- 01most common
Groundwater entering through the tank shell
The tell — Water quality deteriorates after heavy rain, or the level rises unexpectedly.
Underground Water Tank (UGT) Waterproofing → - 02common
Failed internal lining
The tell — Visible deterioration of the internal surface when the tank is emptied.
Food Grade Coating for Water Bodies → - 03common
Unsealed pipe penetrations
The tell — Ingress traces to a specific inlet or outlet position.
Underground Water Tank (UGT) Waterproofing → - 04less common
Cracked shell from settlement
The tell — A visible crack, often at a corner, with staining on the outer face.
Injection Grouting →
Sixty seconds, before you call anyone
- Photograph it while it is actively wet. A dried stain tells a surveyor far less than a running one.
- Note whether it worsens with rain or with usage. Rain-linked points to the building envelope; usage-linked points to plumbing. This single distinction settles most arguments about responsibility.
- Check the area directly above and beside the damage, not only below it. Water travels along a slab before it drops.
- Look specifically for the tell of the most likely cause: water quality deteriorates after heavy rain, or the level rises unexpectedly.
- Do not chip into saturated plaster or paint over a damp patch. The first risks bringing material down; the second destroys the evidence needed to trace the path.
What it becomes if you leave it
Contaminated stored water is a direct health risk to every resident. Beyond that, a leaking underground tank continuously saturates the ground around the structure and undermines adjacent below-grade construction.
This one carries a safety or rapid-escalation risk.
Often seen alongside this
Underground water tank contamination or loss — questions we get asked
What is the most likely cause of underground water tank contamination or loss?
Groundwater entering through the tank shell. The sign that points to it is: water quality deteriorates after heavy rain, or the level rises unexpectedly. That said, the ranking here is a starting point — the actual source is confirmed by survey, because more than one of these can be true at once.
What happens if I leave it?
Contaminated stored water is a direct health risk to every resident. Beyond that, a leaking underground tank continuously saturates the ground around the structure and undermines adjacent below-grade construction.
Can I diagnose this myself before calling anyone?
Partly, and it is worth doing. Photograph it while it is actively wet, note whether it worsens with rain or with usage, and check the area directly above and beside the damage. That single rain-versus-usage distinction narrows the cause more than anything else you can do in sixty seconds.
How urgent is this?
Urgent. This can compound quickly or carries a safety risk. Do not wait for the monsoon to end.
Send us a photograph and we will tell you what we think it is
WhatsApp a photo taken while it is wet, with a note on whether it tracks with rain or with usage. That is usually enough for a first opinion, and the site inspection that follows is free.
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